<!DOCTYPE html>
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	<head>
		<title>three.js webgl - gpgpu - flocking</title>
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		<link type="text/css" rel="stylesheet" href="main.css">
		<style>
			body {
				background-color: #fff;
				color: #444;
			}
			a {
				color:#08f;
			}
		</style>
	</head>
	<body>

		<div id="info">
			<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - webgl gpgpu birds + GLTF mesh<br/>
			Flamingo by <a href="https://mirada.com/" target="_blank" rel="noopener">mirada</a> from <a href="http://www.ro.me/" target="_blank" rel="noopener">rome</a><br/>
			Move mouse to disturb birds.
		</div>

		<!-- shader for bird's position -->
		<script id="fragmentShaderPosition" type="x-shader/x-fragment">

			uniform float time;
			uniform float delta;

			void main()	{

				vec2 uv = gl_FragCoord.xy / resolution.xy;
				vec4 tmpPos = texture2D( texturePosition, uv );
				vec3 position = tmpPos.xyz;
				vec3 velocity = texture2D( textureVelocity, uv ).xyz;

				float phase = tmpPos.w;

				phase = mod( ( phase + delta +
					length( velocity.xz ) * delta * 3. +
					max( velocity.y, 0.0 ) * delta * 6. ), 62.83 );

				gl_FragColor = vec4( position + velocity * delta * 15. , phase );

			}

		</script>

		<!-- shader for bird's velocity -->
		<script id="fragmentShaderVelocity" type="x-shader/x-fragment">

			uniform float time;
			uniform float testing;
			uniform float delta; // about 0.016
			uniform float separationDistance; // 20
			uniform float alignmentDistance; // 40
			uniform float cohesionDistance; //
			uniform float freedomFactor;
			uniform vec3 predator;

			const float width = resolution.x;
			const float height = resolution.y;

			const float PI = 3.141592653589793;
			const float PI_2 = PI * 2.0;
			// const float VISION = PI * 0.55;

			float zoneRadius = 40.0;
			float zoneRadiusSquared = 1600.0;

			float separationThresh = 0.45;
			float alignmentThresh = 0.65;

			const float UPPER_BOUNDS = BOUNDS;
			const float LOWER_BOUNDS = -UPPER_BOUNDS;

			const float SPEED_LIMIT = 9.0;

			float rand( vec2 co ){
				return fract( sin( dot( co.xy, vec2(12.9898,78.233) ) ) * 43758.5453 );
			}

			void main() {

				zoneRadius = separationDistance + alignmentDistance + cohesionDistance;
				separationThresh = separationDistance / zoneRadius;
				alignmentThresh = ( separationDistance + alignmentDistance ) / zoneRadius;
				zoneRadiusSquared = zoneRadius * zoneRadius;


				vec2 uv = gl_FragCoord.xy / resolution.xy;
				vec3 birdPosition, birdVelocity;

				vec3 selfPosition = texture2D( texturePosition, uv ).xyz;
				vec3 selfVelocity = texture2D( textureVelocity, uv ).xyz;

				float dist;
				vec3 dir; // direction
				float distSquared;

				float separationSquared = separationDistance * separationDistance;
				float cohesionSquared = cohesionDistance * cohesionDistance;

				float f;
				float percent;

				vec3 velocity = selfVelocity;

				float limit = SPEED_LIMIT;

				dir = predator * UPPER_BOUNDS - selfPosition;
				dir.z = 0.;
				// dir.z *= 0.6;
				dist = length( dir );
				distSquared = dist * dist;

				float preyRadius = 150.0;
				float preyRadiusSq = preyRadius * preyRadius;


				// move birds away from predator
				if ( dist < preyRadius ) {

					f = ( distSquared / preyRadiusSq - 1.0 ) * delta * 100.;
					velocity += normalize( dir ) * f;
					limit += 5.0;
				}


				// if (testing == 0.0) {}
				// if ( rand( uv + time ) < freedomFactor ) {}


				// Attract flocks to the center
				vec3 central = vec3( 0., 0., 0. );
				dir = selfPosition - central;
				dist = length( dir );

				dir.y *= 2.5;
				velocity -= normalize( dir ) * delta * 5.;

				for ( float y = 0.0; y < height; y++ ) {
					for ( float x = 0.0; x < width; x++ ) {

						vec2 ref = vec2( x + 0.5, y + 0.5 ) / resolution.xy;
						birdPosition = texture2D( texturePosition, ref ).xyz;

						dir = birdPosition - selfPosition;
						dist = length( dir );

						if ( dist < 0.0001 ) continue;

						distSquared = dist * dist;

						if ( distSquared > zoneRadiusSquared ) continue;

						percent = distSquared / zoneRadiusSquared;

						if ( percent < separationThresh ) { // low

							// Separation - Move apart for comfort
							f = ( separationThresh / percent - 1.0 ) * delta;
							velocity -= normalize( dir ) * f;

						} else if ( percent < alignmentThresh ) { // high

							// Alignment - fly the same direction
							float threshDelta = alignmentThresh - separationThresh;
							float adjustedPercent = ( percent - separationThresh ) / threshDelta;

							birdVelocity = texture2D( textureVelocity, ref ).xyz;

							f = ( 0.5 - cos( adjustedPercent * PI_2 ) * 0.5 + 0.5 ) * delta;
							velocity += normalize( birdVelocity ) * f;

						} else {

							// Attraction / Cohesion - move closer
							float threshDelta = 1.0 - alignmentThresh;
							float adjustedPercent;
							if( threshDelta == 0. ) adjustedPercent = 1.;
							else adjustedPercent = ( percent - alignmentThresh ) / threshDelta;

							f = ( 0.5 - ( cos( adjustedPercent * PI_2 ) * -0.5 + 0.5 ) ) * delta;

							velocity += normalize( dir ) * f;

						}

					}

				}

				// this make tends to fly around than down or up
				// if (velocity.y > 0.) velocity.y *= (1. - 0.2 * delta);

				// Speed Limits
				if ( length( velocity ) > limit ) {
					velocity = normalize( velocity ) * limit;
				}

				gl_FragColor = vec4( velocity, 1.0 );

			}

		</script>

		<script type="module">

			import * as THREE from '../build/three.module.js';
			import Stats from './jsm/libs/stats.module.js';
			import { GUI } from './jsm/libs/dat.gui.module.js';
			import { GLTFLoader } from './jsm/loaders/GLTFLoader.js';
			import { GPUComputationRenderer } from './jsm/misc/GPUComputationRenderer.js';

			/* TEXTURE WIDTH FOR SIMULATION */
			const WIDTH = 64;
			const BIRDS = WIDTH * WIDTH;

			/* BAKE ANIMATION INTO TEXTURE and CREATE GEOMETRY FROM BASE MODEL */
			const BirdGeometry = new THREE.BufferGeometry();
			let textureAnimation, durationAnimation, birdMesh, materialShader, vertexPerBird;

			function nextPowerOf2( n ) {

				return Math.pow( 2, Math.ceil( Math.log( n ) / Math.log( 2 ) ) );

			}

			Math.lerp = function ( value1, value2, amount ) {

				amount = Math.max( Math.min( amount, 1 ), 0 );
				return value1 + ( value2 - value1 ) * amount;

			};

			const gltfs = [ 'models/gltf/Parrot.glb', 'models/gltf/Flamingo.glb' ];
			const colors = [ 0xccFFFF, 0xffdeff ];
			const sizes = [ 0.2, 0.1 ];
			const selectModel = Math.floor( Math.random() * gltfs.length );
			new GLTFLoader().load( gltfs[ selectModel ], function ( gltf ) {

				const animations = gltf.animations;
				durationAnimation = Math.round( animations[ 0 ].duration * 60 );
				const birdGeo = gltf.scene.children[ 0 ].geometry;
				const morphAttributes = birdGeo.morphAttributes.position;
				const tHeight = nextPowerOf2( durationAnimation );
				const tWidth = nextPowerOf2( birdGeo.getAttribute( 'position' ).count );
				vertexPerBird = birdGeo.getAttribute( 'position' ).count;
				const tData = new Float32Array( 3 * tWidth * tHeight );

				for ( let i = 0; i < tWidth; i ++ ) {

					for ( let j = 0; j < tHeight; j ++ ) {

						const offset = j * tWidth * 3;

						const curMorph = Math.floor( j / durationAnimation * morphAttributes.length );
						const nextMorph = ( Math.floor( j / durationAnimation * morphAttributes.length ) + 1 ) % morphAttributes.length;
						const lerpAmount = j / durationAnimation * morphAttributes.length % 1;

						if ( j < durationAnimation ) {

							let d0, d1;

							d0 = morphAttributes[ curMorph ].array[ i * 3 ];
							d1 = morphAttributes[ nextMorph ].array[ i * 3 ];

							if ( d0 !== undefined && d1 !== undefined ) tData[ offset + i * 3 ] = Math.lerp( d0, d1, lerpAmount );

							d0 = morphAttributes[ curMorph ].array[ i * 3 + 1 ];
							d1 = morphAttributes[ nextMorph ].array[ i * 3 + 1 ];

							if ( d0 !== undefined && d1 !== undefined ) tData[ offset + i * 3 + 1 ] = Math.lerp( d0, d1, lerpAmount );

							d0 = morphAttributes[ curMorph ].array[ i * 3 + 2 ];
							d1 = morphAttributes[ nextMorph ].array[ i * 3 + 2 ];

							if ( d0 !== undefined && d1 !== undefined ) tData[ offset + i * 3 + 2 ] = Math.lerp( d0, d1, lerpAmount );

						}

					}

				}

				textureAnimation = new THREE.DataTexture( tData, tWidth, tHeight, THREE.RGBFormat, THREE.FloatType );
				textureAnimation.needsUpdate = true;

				const vertices = [], color = [], reference = [], seeds = [], indices = [];
				const totalVertices = birdGeo.getAttribute( 'position' ).count * 3 * BIRDS;
				for ( let i = 0; i < totalVertices; i ++ ) {

					const bIndex = i % ( birdGeo.getAttribute( 'position' ).count * 3 );
					vertices.push( birdGeo.getAttribute( 'position' ).array[ bIndex ] );
					color.push( birdGeo.getAttribute( 'color' ).array[ bIndex ] );

				}

				let r = Math.random();
				for ( let i = 0; i < birdGeo.getAttribute( 'position' ).count * BIRDS; i ++ ) {

					const bIndex = i % ( birdGeo.getAttribute( 'position' ).count );
					const bird = Math.floor( i / birdGeo.getAttribute( 'position' ).count );
					if ( bIndex == 0 ) r = Math.random();
					const j = ~ ~ bird;
					const x = ( j % WIDTH ) / WIDTH;
					const y = ~ ~ ( j / WIDTH ) / WIDTH;
					reference.push( x, y, bIndex / tWidth, durationAnimation / tHeight );
					seeds.push( bird, r, Math.random(), Math.random() );

				}

				for ( let i = 0; i < birdGeo.index.array.length * BIRDS; i ++ ) {

					const offset = Math.floor( i / birdGeo.index.array.length ) * ( birdGeo.getAttribute( 'position' ).count );
					indices.push( birdGeo.index.array[ i % birdGeo.index.array.length ] + offset );

				}

				BirdGeometry.setAttribute( 'position', new THREE.BufferAttribute( new Float32Array( vertices ), 3 ) );
				BirdGeometry.setAttribute( 'birdColor', new THREE.BufferAttribute( new Float32Array( color ), 3 ) );
				BirdGeometry.setAttribute( 'color', new THREE.BufferAttribute( new Float32Array( color ), 3 ) );
				BirdGeometry.setAttribute( 'reference', new THREE.BufferAttribute( new Float32Array( reference ), 4 ) );
				BirdGeometry.setAttribute( 'seeds', new THREE.BufferAttribute( new Float32Array( seeds ), 4 ) );

				BirdGeometry.setIndex( indices );

				init();
				animate();

			} );

			let container, stats;
			let camera, scene, renderer;
			let mouseX = 0, mouseY = 0;

			let windowHalfX = window.innerWidth / 2;
			let windowHalfY = window.innerHeight / 2;

			const BOUNDS = 800, BOUNDS_HALF = BOUNDS / 2;

			let last = performance.now();

			let gpuCompute;
			let velocityVariable;
			let positionVariable;
			let positionUniforms;
			let velocityUniforms;

			function init() {

				container = document.createElement( 'div' );
				document.body.appendChild( container );

				camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 3000 );
				camera.position.z = 350;

				scene = new THREE.Scene();
				scene.background = new THREE.Color( colors[ selectModel ] );
				scene.fog = new THREE.Fog( colors[ selectModel ], 100, 1000 );

				// LIGHTS

				const hemiLight = new THREE.HemisphereLight( colors[ selectModel ], 0xffffff, 1.6 );
				hemiLight.color.setHSL( 0.6, 1, 0.6 );
				hemiLight.groundColor.setHSL( 0.095, 1, 0.75 );
				hemiLight.position.set( 0, 50, 0 );
				scene.add( hemiLight );

				const dirLight = new THREE.DirectionalLight( 0x00CED1, 0.6 );
				dirLight.color.setHSL( 0.1, 1, 0.95 );
				dirLight.position.set( - 1, 1.75, 1 );
				dirLight.position.multiplyScalar( 30 );
				scene.add( dirLight );

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				container.appendChild( renderer.domElement );

				initComputeRenderer();

				stats = new Stats();
				container.appendChild( stats.dom );

				container.style.touchAction = 'none';
				container.addEventListener( 'pointermove', onPointerMove );

				window.addEventListener( 'resize', onWindowResize );

				const gui = new GUI();

				const effectController = {

					separation: 20.0,
					alignment: 20.0,
					cohesion: 20.0,
					freedom: 0.75,
					size: sizes[ selectModel ],
					count: BIRDS

				};

				const valuesChanger = function () {

					velocityUniforms[ "separationDistance" ].value = effectController.separation;
					velocityUniforms[ "alignmentDistance" ].value = effectController.alignment;
					velocityUniforms[ "cohesionDistance" ].value = effectController.cohesion;
					velocityUniforms[ "freedomFactor" ].value = effectController.freedom;
					if ( materialShader ) materialShader.uniforms[ "size" ].value = effectController.size;
					BirdGeometry.setDrawRange( 0, vertexPerBird * effectController.count );

				};

				valuesChanger();

				gui.add( effectController, "separation", 0.0, 100.0, 1.0 ).onChange( valuesChanger );
				gui.add( effectController, "alignment", 0.0, 100, 0.001 ).onChange( valuesChanger );
				gui.add( effectController, "cohesion", 0.0, 100, 0.025 ).onChange( valuesChanger );
				gui.add( effectController, "size", 0, 1, 0.01 ).onChange( valuesChanger );
				gui.add( effectController, "count", 0, BIRDS, 1 ).onChange( valuesChanger );
				gui.close();

				initBirds( effectController );

			}

			function initComputeRenderer() {

				gpuCompute = new GPUComputationRenderer( WIDTH, WIDTH, renderer );

				if ( isSafari() ) {

					gpuCompute.setDataType( THREE.HalfFloatType );

				}

				const dtPosition = gpuCompute.createTexture();
				const dtVelocity = gpuCompute.createTexture();
				fillPositionTexture( dtPosition );
				fillVelocityTexture( dtVelocity );

				velocityVariable = gpuCompute.addVariable( "textureVelocity", document.getElementById( 'fragmentShaderVelocity' ).textContent, dtVelocity );
				positionVariable = gpuCompute.addVariable( "texturePosition", document.getElementById( 'fragmentShaderPosition' ).textContent, dtPosition );

				gpuCompute.setVariableDependencies( velocityVariable, [ positionVariable, velocityVariable ] );
				gpuCompute.setVariableDependencies( positionVariable, [ positionVariable, velocityVariable ] );

				positionUniforms = positionVariable.material.uniforms;
				velocityUniforms = velocityVariable.material.uniforms;

				positionUniforms[ "time" ] = { value: 0.0 };
				positionUniforms[ "delta" ] = { value: 0.0 };
				velocityUniforms[ "time" ] = { value: 1.0 };
				velocityUniforms[ "delta" ] = { value: 0.0 };
				velocityUniforms[ "testing" ] = { value: 1.0 };
				velocityUniforms[ "separationDistance" ] = { value: 1.0 };
				velocityUniforms[ "alignmentDistance" ] = { value: 1.0 };
				velocityUniforms[ "cohesionDistance" ] = { value: 1.0 };
				velocityUniforms[ "freedomFactor" ] = { value: 1.0 };
				velocityUniforms[ "predator" ] = { value: new THREE.Vector3() };
				velocityVariable.material.defines.BOUNDS = BOUNDS.toFixed( 2 );

				velocityVariable.wrapS = THREE.RepeatWrapping;
				velocityVariable.wrapT = THREE.RepeatWrapping;
				positionVariable.wrapS = THREE.RepeatWrapping;
				positionVariable.wrapT = THREE.RepeatWrapping;

				const error = gpuCompute.init();

				if ( error !== null ) {

					console.error( error );

				}

			}

			function isSafari() {

				return !! navigator.userAgent.match( /Safari/i ) && ! navigator.userAgent.match( /Chrome/i );

			}

			function initBirds( effectController ) {

				const geometry = BirdGeometry;

				const m = new THREE.MeshStandardMaterial( {
					vertexColors: true,
					flatShading: true,
					roughness: 1,
					metalness: 0
				} );

				m.onBeforeCompile = ( shader ) => {

					shader.uniforms.texturePosition = { value: null };
					shader.uniforms.textureVelocity = { value: null };
					shader.uniforms.textureAnimation = { value: textureAnimation };
					shader.uniforms.time = { value: 1.0 };
					shader.uniforms.size = { value: effectController.size };
					shader.uniforms.delta = { value: 0.0 };

					let token = '#define STANDARD';

					let insert = /* glsl */`
						attribute vec4 reference;
						attribute vec4 seeds;
						attribute vec3 birdColor;
						uniform sampler2D texturePosition;
						uniform sampler2D textureVelocity;
						uniform sampler2D textureAnimation;
						uniform float size;
						uniform float time;
					`;

					shader.vertexShader = shader.vertexShader.replace( token, token + insert );

					token = '#include <begin_vertex>';

					insert = /* glsl */`
						vec4 tmpPos = texture2D( texturePosition, reference.xy );

						vec3 pos = tmpPos.xyz;
						vec3 velocity = normalize(texture2D( textureVelocity, reference.xy ).xyz);
						vec3 aniPos = texture2D( textureAnimation, vec2( reference.z, mod( time + ( seeds.x ) * ( ( 0.0004 + seeds.y / 10000.0) + normalize( velocity ) / 20000.0 ), reference.w ) ) ).xyz;
						vec3 newPosition = position;

						newPosition = mat3( modelMatrix ) * ( newPosition + aniPos );
						newPosition *= size + seeds.y * size * 0.2;

						velocity.z *= -1.;
						float xz = length( velocity.xz );
						float xyz = 1.;
						float x = sqrt( 1. - velocity.y * velocity.y );

						float cosry = velocity.x / xz;
						float sinry = velocity.z / xz;

						float cosrz = x / xyz;
						float sinrz = velocity.y / xyz;

						mat3 maty =  mat3( cosry, 0, -sinry, 0    , 1, 0     , sinry, 0, cosry );
						mat3 matz =  mat3( cosrz , sinrz, 0, -sinrz, cosrz, 0, 0     , 0    , 1 );

						newPosition =  maty * matz * newPosition;
						newPosition += pos;

						vec3 transformed = vec3( newPosition );
					`;

					shader.vertexShader = shader.vertexShader.replace( token, insert );

					materialShader = shader;

				};

				birdMesh = new THREE.Mesh( geometry, m );
				birdMesh.rotation.y = Math.PI / 2;

				birdMesh.castShadow = true;
				birdMesh.receiveShadow = true;

				scene.add( birdMesh );

			}

			function fillPositionTexture( texture ) {

				const theArray = texture.image.data;

				for ( let k = 0, kl = theArray.length; k < kl; k += 4 ) {

					const x = Math.random() * BOUNDS - BOUNDS_HALF;
					const y = Math.random() * BOUNDS - BOUNDS_HALF;
					const z = Math.random() * BOUNDS - BOUNDS_HALF;

					theArray[ k + 0 ] = x;
					theArray[ k + 1 ] = y;
					theArray[ k + 2 ] = z;
					theArray[ k + 3 ] = 1;

				}

			}

			function fillVelocityTexture( texture ) {

				const theArray = texture.image.data;

				for ( let k = 0, kl = theArray.length; k < kl; k += 4 ) {

					const x = Math.random() - 0.5;
					const y = Math.random() - 0.5;
					const z = Math.random() - 0.5;

					theArray[ k + 0 ] = x * 10;
					theArray[ k + 1 ] = y * 10;
					theArray[ k + 2 ] = z * 10;
					theArray[ k + 3 ] = 1;

				}

			}

			function onWindowResize() {

				windowHalfX = window.innerWidth / 2;
				windowHalfY = window.innerHeight / 2;

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			function onPointerMove( event ) {

				if ( event.isPrimary === false ) return;

				mouseX = event.clientX - windowHalfX;
				mouseY = event.clientY - windowHalfY;

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				render();
				stats.update();

			}

			function render() {

				const now = performance.now();
				let delta = ( now - last ) / 1000;

				if ( delta > 1 ) delta = 1; // safety cap on large deltas
				last = now;

				positionUniforms[ "time" ].value = now;
				positionUniforms[ "delta" ].value = delta;
				velocityUniforms[ "time" ].value = now;
				velocityUniforms[ "delta" ].value = delta;
				if ( materialShader ) materialShader.uniforms[ "time" ].value = now / 1000;
				if ( materialShader ) materialShader.uniforms[ "delta" ].value = delta;

				velocityUniforms[ "predator" ].value.set( 0.5 * mouseX / windowHalfX, - 0.5 * mouseY / windowHalfY, 0 );

				mouseX = 10000;
				mouseY = 10000;

				gpuCompute.compute();

				if ( materialShader ) materialShader.uniforms[ "texturePosition" ].value = gpuCompute.getCurrentRenderTarget( positionVariable ).texture;
				if ( materialShader ) materialShader.uniforms[ "textureVelocity" ].value = gpuCompute.getCurrentRenderTarget( velocityVariable ).texture;

				renderer.render( scene, camera );

			}

		</script>
	</body>
</html>
